In the manufacture of thin film integrated circuits, substrates in the form of rectangular ceramic wafers are (1) transferred from a magazine into a sputtering chamber within which a thin coating of metal is sputtered onto the substrates, (2) transferred on completion of the sputtering back to a magazine and then (3) processed by the use of photolithographic and other techniques to convert such coated substrates into such circuits.
Sputtering of the metal coating onto the substrates is effected within the mentioned chamber by: maintaining a vacuum therein and providing therein a negatively charged sputtering cathode which ionizes the rarefied arson atmosphere which, in turn, erodes the metal cathode causing such metal to be deposited on the substrates, and exposing the substrates to such deposition for a predetermined time so as to render the metal coating thereon of a predetermined desired thickness. Such fixed time of exposure is obtained by positioning the substrates seriatim at the sides of a polygonal stepwise-rotatable cage in the chamber, and by indexing the cage step-by-step so as to move the substrates in the chamber for a fixed time along a fixed length path which begins at a transfer station at which the uncoated substrates originally enter the chamber, and which closes on itself to eventually return to such station from which the now coated substrates are then removed from such chamber. An elevator mechanism is commonly used for conveying uncoated substrates to the chamber from a magazine and for conveying the coated substrates from the chamber back to a magazine.
The original cylindrical sputtering machines made use of two elevators. The lower elevator pushed the tray up from the main chamber into the sputtering chamber and supported the tray as the cage indexed. The upper elevator pushed the tray down from the sputtering chamber into the magazine in the lower chamber. As an improvement, cylindrical sputtering machines developed earlier by others have made use of only one elevator in which the functions of the two previous elevators were combined. The single elevator design simplified maintenance and improved reliability. It too, however, had its shortcomings resulting from the elevator and tray tab and other designs.